Effect of a single dose of primaquine on a Thai strain of Plasmodium falciparum.

A single dose of 45 mg of primaquine base was effective in the elimination of gametocytes of the possibly chloroquine-resistant P. falciparum in Thailand. The gametocyte counts decreased markedly within 3.5 days showing significantly difference from the control in which mostly gametocytes still remain within 11.4 days. The development of the gametocytes in A. dirus was not observed after treatment. Primaquine can be used as gametocytocide and sporontocide for falciparum malaria in Thailand if the drug is administered when matured gametocytes appeared in the peripheral blood.